Carry Dodge Roll and Ragonok. Also, carry a lot of items as you need it often.

Step 1

Before he uses his Spell Binder, use Aeroga to shield.Hit the dark orbs on his hands. Use Ragonok Impact to attack both. BIG HP balls and items will pop out of defeated hands. Use Dodge Roll to avoid Flying Blades later on, after wearing it down.

Step 2

(cast Tinker Bell if first time) Use Thunderga on shield. Good time use spells like Aeroga for step 1.

After dark orbs are destoryed or shield depleted, attack his head. Good time to heal up. Win? Exp. and journal entry! Whoo-Yoo!

You got a ton of Heartless to deal with, so just fight them all as you move down the street. Keep on truckin' till you get to the Memory's Skyscraper. Survey the area for chests, and head on to The Brink of Despair. Cross the bridge into Nothing's Call. Follow this on to Crooked Ascension and Twilight's View. Eventually you'll meet your first bad ass of this world.

Xigbar can be intimidating because he has the advantage of warping all over the damn place. It hardly seems fair, but deal with it. And you will if you remember to press that TRIANGLE BUTTON when you seem him sniping you from afar. This reflects his shots right back at him, at which point he'll abandon sniping and come down to fight you. The key to this portion is to continue to use TRIANGLE to warp around the arena to hit this guy. If the fact that he has a gun isn't harsh enough, he'll actually change the shape of the floor throughout the battle, and shower you with bullets (or whatever the hell they are). Cast reflect when he does this to protect yourself, and as soon as you see an opening, just unleash on him with combos. It's never too late to use a Drive form at any point. The best ones are the ones that make use of melee attacks, so that's Valor and Master Form. When he starts to feel the pain, he'll try sniping again, just use TRIANGLE to deal with that. He can be tough, but you can take him.

When Xigbar is finished, head outside and up the skyway, fighting vicious Nobodies all along the way. Head around the corner and back into the hall and look... Kairi. She has someone else with her but wait, is that... psyche!

Now head on into Proof of Existence. When you access Havoc's Divide, it's time to deal with Luxord. You have to fight him by yourself and it can get rather weird. At the beginning you're a die piece. Just bounce over to him and by hitting the CIRCLE BUTTON, and try to hit him. When you break free, you're only objective is to save time. Whoever runs out of time first will lose. He'll turn into a card and you have to follow and mix himself up with a wall of spinning cards. You have to follow which one you think is him and use the TRIANGLE BUTTON on it, then attack. You can also use TRIANGLE to initiate Begin Game. The Attack, Magic, Items, and Drive button turn into X's and O's. Try to hit the CIRCLE as it rotates down. If you miss it, you turn back into a die. Keep at it, and some how you'll win.

Saix isn't so hard to deal with. Yeah de does his Berserk thing when his meter fills up, but all you have to do is avoid him when this happens and that's not hard to do. The best plan of action is to hit your drive form when he's in his Beserk state, especially because you replenish life that way. If you have Final Form at this point, you can glide out of the way when he's going crazy. Things might look scary late in the battle because his berserk attack get stronger as his life diminishes, but don't let him push you around. Grab his weapons, run over to him and hit TRIANGLE knock him back into his senses. Outside of that, use your combos and he will die.

Now go back in the Proof of Existence. you will be finishing up some plot points which ends in your old homie Riku joining up with the gang. Kill all the Heartless that confront you, going from platform to platform. At the end, you'll get another helping hand from Maleficent, but with Pete helping out too this time. Now you can go on ahead and face the next challenge.

Go forth and face Xemnas. This first sampler is just you against him so you don't have use of any of your drive forms. You're teleport over to the front of the Memory Skyscraper, and Xemnas will start off playing dirty by trapping you in these crystals that start to hurt. Run to the front of the Memory Skyscraper and use TRIANGLE to fix it. Then Xemnas tried to get tight like Yoda and Darth Maul and start attacking you with has dual light sabers. He's fast but don't let him punk you. Fight back with just as much aggression. He'll go invincible when he's shrouded in darkness. Wait for the opportune moment and attack again. When he summon his shields, hit him from the side. Stick to the pattern and mind your health. He give up in no time. But of course, it's far from over. He will then proceed through a door and your expected to follow. Make sure you've finished everything else you want to do in the game, like side missions, fighting Sephiroth, getting the Fenrir, getting the Ultima Weapon, and all the Jiminy Journal stuff. When you feel you're ready, go ahead and go through the door.

This next section is basically it's own level. But it's not that hard. For the first part, you have to get pass some buildings that are springing from the ground. Just run up and hit TRIANGLE when you're told to do so. Next, you'll face off against some nobodies. Again, when the TRIANGLE indicator pops up, hit the button and move out the way of a huge energy blast. You do this a few times before it's all over. Defeat all the Nobodies and move on. Now you have to deal with this hostile energy core. It will find a way to attack you with spikes, but just jump. A shield will appear to protect it, but I noticed that shields at this point are little help to your enemies because they're only up for a sec.When the Nobodies show-up, kill them all and commit yourself to the energy core again. Moving on.

Now you go up against Xemnas who appears as an armored king on a throne. The key thing to remember is you can always punish this guy with the new limit attack called Session that Riku will join you to accomplish. He'll hit you and summon a shield every now and then, but press on.

When you deplete his life, the ground will fall away and you'll have to face a dragon like contraption. Riku and Sora hop on a machine of their own, and shoot at the beast as you would in the Gummi ship trial. The exception is that if you hit the CIRCLE button, you can drain energy from lasers shot at the ship. Fill up the ENERGY meter, and a TRIANGLE BUTTON prompt will appear to prompt you to use Megalaser blast that packs an enormous punch. The background will shift to have you attack the dragon from different angles. Keep the lasers coming and move on.

Next, Xemnas is back in his throne as the armored king again. At this point Sora and Riku have swatted into space, and you have to glide back to the battle area to take on Xemnas. The only problem is that Xemnas is hurling buildings at you like Jafar. Hit SQUARE to glide forward, and CIRCLE to soar higher. Aim for the stationary building you'll see in the distance, when you get close enough, you'll get another TRIANGLE prompt. Hit the button and you and Riku will pull off a fancy move that breaks the shield that Xemnas is hiding behind, which allows you to come down and fight him. Get close enough, and handle him the way you did before by delivering that Session limit attack as often as possible. He will at long last give in.

Ok, now you get to fight this fool face to face. No more dragons or armor. After he finishes running his mouth, he'll come after Sora directly and Riku will jump in and protect him. Fight Xemnas as aggressively as possible. He'll send his squirrelly barbed wire at you, but use TRIANGLE to evade it the way Roxas did against the giant Nobody in the beginning of the game. When he starts sending lasers at you, just block that crap with SQUARE. If your energy dips, Riku will throw some potion your way. Let him, because honestly, you want to save your magic to deliver Session Limit attacks at Xemnas. Lock-on and hit Xemnas with Session as soon as your magic bar fills up. Guide Sora so that he stays on him too, because you want to deliver as many hits with the attack as possible. When Xemnas gets weak enough, he'll pull some punk s***, grab Sora and slowly deplete his HP.

At this point you take over Riku, and you have to get to Sora before he dies. Only problem is Xemnas clones himself and tries to stop you by throwing up these shields that knock you backward. Take control of the camera and run at Xemnas and Sora from the side, jumping to avoid the shields. When you're close enough, hit TRIANGLE. This frees Sora and you can control him again. A few more limit attacks later, Xemnas is feeling the burn. It's then that he'll pull his cheapest move yet, and surround Riku and Sora in a dome floating laser beams. All of them start coming at you. All you have to do is hit the TRIANGLE and X BUTTONS back and forth, back and forth, in a fast but steady pace. Sora and Riku will block all the lasers! Succeed, and the games is done. Xemnas reappears all weak and beat up. Run up and smash him, and a story sequence will finish things.